Amazon GC question?

I placed an order for a DVD that cost about $17.00 at Amazon and used the $10 Promo coupon code that was mailed out via USMail a few weeks back. On checking the status though the $10 coupon wasn't applied though it said it was when I placed the order initially. After emailing Amazon, now they tell me that if I look in the fine print it makes mention of a $20 minimum purchase and for that reason they can't apply it. I have looked through the entire flyer and there is no mention of a minimum purchase anywhere. Has this happened to anyone else out there?